An orthodontic appliance equipped with an orthodontic wire to be mounted on teeth has been conventionally known. An elastic restoring force of the orthodontic wire acts as a constant static load on the teeth to correct teeth malalignment or crossbite. In other words, the orthodontic appliance is based on the principle of aligning the teeth by gradually deforming an alveolar bone supporting the teeth in the gum (bone reconstruction, bone remodeling) through the application of a constant force to the teeth.
However, the teeth alignment using the orthodontic wire takes a very long time (fastest six months, normally several years) until an orthodontic treatment is finished. Such a long treatment period increases burdens on patients, causing them to give up easily.
In order to shorten a period of such an orthodontic treatment, technology of giving a vibration force to the teeth has been studied. For example, a study result to the effect that if a sample A in which a constant force was applied to the teeth and a sample B in which a vibration force was applied to the teeth are compared, the sample B in which the vibration force was applied is more effective in shortening the period as shown in FIG. 7A is disclosed in Non-Patent Literature 1. Similarly, a study result to the effect that if a sample C in which a constant force was applied to the teeth and a sample D in which a constant force and a vibration force were applied to the teeth are compared, the sample D in which the constant force and vibration force were applied is more effective in shortening the period as shown in FIG. 7B is disclosed in non-Patent Literature 2.
According to these studies, the application of the vibration force to the teeth remarkably shortens the period of orthodontic treatment to about ½ to ⅓ as compared to conventional technologies. Further, it is sufficient to apply a vibration force only for 1.5 hours a day according to the former literature and only for 2 minutes at a time and once every two weeks according to the latter literature.
It can be understood from these studies that the teeth alignment by applying a vibration force as well as a constant force to the teeth is more effective in remarkably shortening the period of orthodontic treatment than the teeth alignment only by applying a constant force to the teeth using an orthodontic wire or the like.
Appliances for putting the above studies to practical use have been conventionally proposed. Specifically, Patent Literature 1 discloses an appliance provided with a dental mouthpiece to be mounted on teeth to urge movements of teeth to be aligned and means for applying ultrasonic vibration to tissues surrounding the mounted position of the dental mouthpiece. Further, Patent Literature 2 discloses an appliance for applying ultrasonic vibration to teeth to be aligned.
However, the appliances disclosed in the above Patent Literatures 1, 2 have a problem that ultrasonic vibration cannot be efficiently applied to the teeth to be aligned since both of them receive the application of ultrasonic vibration from the outside, for example, by pressing an ultrasonic head against the cheek skin. Further, since the respective appliances require an ultrasonic generator, there is also a problem that treatment cannot be continued unless a patient goes to a dental clinic equipped with these appliances.    [Non-Patent Literature 1] Shimizu: “Journal of Japan Orthodontic Society” 45, pp. 56-72, 1986    [Non-Patent Literature 2] Ohmae et al.: “Journal of Japan Orthodontic Society” 60(4), p. 201, 2001    [Patent Literature 1] Japanese Unexamined Patent Publication No. 2002-102255    [Patent Literature 2] Japanese Unexamined Patent Publication No. 2004-201895